Outdoor lighting equipment



1966 J. T BARNES 3,284,625

OUTDOOR LIGHTING EQUIPMENT Filed May 8, 1964 I N V E NTOR. LV '7'; $ARNES BY 6 @MP ATTOR NEYS United States Patent 3,284,625 OUTDOOR LIGHTING EQUIPMENT Jocelyn T. Barnes, Redford Township, Wayne County, Mich., assignor to Lexa Lite Corporation, Southfield, Mich, a corporation of Michigan Filed May 8, 1964, Ser. No. 366,000 Claims. (Cl. 240-25) This invention relates generally to equipment for illuminating private or public outdoor areas, streets, and highways. In such equipment, the assembly which comprises the lightbulb or lamp, its accessory equipment, and the glassware is referred to as a luminaire. The invention particularly relates to improvements in the glassware of a luminaire. The glassware referred to is for the purpose of diffusing light from the light source or refracting it into desired light patterns. Conventionally, this glassware, as the name implies, has been made of glass and is relatively easily cracked or shattered. In urban areas, it is not unusual for public utitlities to spend tens of thousands of dollars each month to replace glassware damaged or destroyed by vandalism. Heretofore, glassware has been made of certain plastic materials. This has not proved satisfactory primarily because the materials used become yellow in time under the effects of ultraviolet radiation received from the light source. This disadvantage is aggravated where the light source is a mercury vapor lamp.

It is possible to slow down this yellowing effect by adding ultraviolet stabilizers to the plastic material but this weakens the plastic material and only delays the time when the glassware must be replaced because of yellowing.

The object of this invention is to provide a simple, relatively inexpensive improved structure which largely eliminates the problems and disadvantages mentioned above.

In general, the invention contemplates making the globe or refractor from a plastic material of suflicient thickness so that it will withstand the abuse of thrown rocks, sling shots, B-B guns, and the like. Within the globe or refractor is an insert made of a thin film of plastic material. This insert conforms to the interior configuration of the globe or refractor and transmits light thereto in undiifused and unrefracted condition. The insert in opaque to ultraviolet radiation which would yellow the globe or refractor. When the insert itself becomes yellowed, it can be removed, disposed of, and a new one substituted in its place. In the accompanying drawings:

FIG. 1 is a partly diagrammatic side elevation of outdoor lighting equipment utilizing the present invention.

FIG. 2 is an enlarged partly diagrammatic generally elevational view of a luminaire incorporating the present invention, portions being shown in section and in phantom to illustrate structural details.

FIG. 3 is an exploded generally perspective view of two components of glassware according to this invention.

FIG. 4 is a fragmentary partly diagrammaatic sectional View on an enlarged scale taken on line 4-4 of FIG. 2.

FIG. 5 is a view similar to FIG. 2 but showing a different type of luminaire incorporating the present invention.

Shown in the drawings is an outdoor lighting fixture comprising a luminaire 12 mounted on a pole 13. Except for the glassware, luminaire 12 is of conventional construction, having a housing 14 which supports a socket 16 and accessory equipment (not shown) for a lamp 18 which, in the illustrated equipment, is a mercury vapor lamp. The luminaire also includes a reflector 20 at the base of which is a conventional wedge band 22 which supports a globe 24 according to this invention.

' and the wedge band Globe 24 comprises an outer element 26 and an inner liner element 28. Outer element 26 is made of a tough, translucent plastic material such as an acrylic, butyrate, or polycarbonate plastic material. An example of a suitable commercially available acrylic plastic is Plexiglas, a product of Rohm and Haas, of Philadelphia, Pa. An example of a suitable commercially available butyrate plastic material is Tenite II, a product of Eastman Chemical Products, Inc., of Kingsport, Tenn. Examples of suitable commercially available polycarbonate plastic materials are Lexan, which is a product of Chemical Materials Department, General Electric Co., Pittsfield, Mass; and Merlon, which is a product of Mobay Chemical Company, of Pittsburgh, Pa. Examples of suitable materials for liner element 28 are the acrylic and polycarbonate materials referred to above.

There may be other plastic materials which are suitable for elements 26 and 28. The principal requirements for the material of outer element 26 are that the material be translucent, tough enough to withstand abuse of thrown rocks, sling shots, B-B guns, and the like when formed into hollow globes or refractors, and resistant to deterioration upon continued exposure to the elements. In general, the polycarbonate materials referred to above meet these requirements more eflfectively than other plastic materials to date tested by applicant.

The requirements for the material forming liner element 28 are that it be translucent, opaque in relatively thin films to ultraviolet light, and resistant: to harmful effects of the heat within globe 24, which may reach about 240 F. Polycarbonate materials have in general met these requirements more effectively than other materials to date tested by applicant. However, Where the luminaire is to be subjected to extremely cold conditions, an acrylic liner may be preferable. In most applications, it is contemplated that the material of liner 28 will be clear and substantially free of diffusing or refracting irregularities. However, the liner material may be: tinted or provided with optical properties as required in specific applications.

When elements 26 and 28 are nested, liner 28 fits closely but loosely within outer element 26 and flanges 30 and 32' at their respective upper edges are interengaged. To mount the assembled elements, their superposed flanges are engaged within wedge band 22 as shown in FIG. 2 is then tightened by means of a threaded clamp 34. In the globe illustrated,'element 26 has an outer side 36 which is smooth and an inner side 38 provided with small diffusing prisms as shown in FIG. 4. Liner 28 is disposed between outer element 26 and lamp 18.

In a commercially satisfactory unit, outer element 26 is formed out of a polycarbonate plastic material and has a wall thickness of about .080. The outer element is formed by injection molding. Liner 28 is also formed of a polycarbonate plastic material. Its wall has a minimum thickness of about .001" but may be considerably thicker depending on whether the cost of the plastic is a material factor in manufacture. A commercially satisfactory liner 28 is made by vacuum molding a film of polycarbonate material which is about .008" thick to begin with, the resulting liner having a thickness ranging down to .002" or .003".

Where liner 28 is made of an acrylic plastic material, its wall thickness in general must be somewhat thicker than that of a liner made of polycarbonate plastic material since the acrylic plastic is not as tough in thin films as the polycarbonate plastic and is somewhat more difficult to handle. In a commercially satisfactory unit, an acrylic liner has a wall thickness of about .010" to .012".

In use, liner 28 has sufficient thickness to be opaque to ultraviolet radiation from lamp 18 which would yellow the wall of outer globe element 26. In time, liner 28 itself becomes yellowed, but when this happens wedge band 22 is merely removed, the old liner disposed of, and a new one added in its place. Original outer element 26 continues in use. The cost of a liner 28 is but a very small fraction of the cost of outer globe member 26.

The close but loose fit of liner 28 within the outer globe element provides a thin insulating air space 40 shown in exaggerated form in FIGS. 2 and 4. This space is thin enough to permit adequate heat dissipation to prevent the interior of the luminaire from becoming overheated but is also adequate to protect outer element 26 from the heat of lamp 18. Since liner 28 is very thin and relatively flexible, it may contact the inner light diffusing prisms of outer element 26 at some locations. However, these regions of contact are very limited and the insulating air space is adequate for the purposes described.

Since liner 28 over the major portion of its area is out of actual contact with the interior of outer element 26, it is relatively invisible from the outside. In actual use, it has been found that it takes at least fifty percent longer for the liner to become objectionably yellowed than it would take for an unlined element 26 to become visibly yellowed to an objectionable extent. This means that the acceptable life of a liner is at least fifty percent longer than would be the acceptable life of an unlined element 26. Where a film material used to make liner 28 is provided with an additive to stabilize it against the eflects of ultraviolet light, the effective life of the liner can be even further increased.

Originally, it was expected that the use of liner 28 would result in a light transmission loss of about 6 percent. In actual use, this has not happened. The actual light transmission loss is only about one percent utilizing either the acrylic or polycarbonate liner. This eflect is not thoroughly understood, but it is believed that the wasted light is ultimately reflected out of the luminaire by reflector 20.

Liner 28 is substantially imperforate and provides a shield or dust pan which protects interior 38 of outer element 26 from accumulations of dust, dirt, and other foreign matter. This either eliminates or greatly reduces the necessity of periodically washing the interior of outer element 26.

Shown in FIG. is a horizontal burning luminaire having a reflector 44 which houses a bulb 46 and its socket 48. The glassware 50 is constructed similarly to globe 24 except for having appropriate configuration and optical characteristics for a horizontal burning luminaire. Glassware 50 has an outer element 52 corresponding to outer element 26 and a liner 54 corresponding to liner 28, these elements cooperating in the manner described above.

I claim:

1. For a luminaire having a light source and light-transmitting means held by support means in light-transmitting relation to the light source, improved light-transmitting means comprising,

a bowl-shaped, form-retaining element made of a tough,

weather-resistant, translucent plastic material, said element having an inner side and an outer side,

a bowl-shaped film made of a heat-resistant, translucent plastic material, said film having a thickness of at least about 1 mil and being substantially opaque to ultraviolet radiation,

said film being separate from said element and being removably insertable within said element,

said element and film being dimensioned and configured to be mounted in light-transmitting relation to the light source of a luminaire with which they are adapted to be used with said inner side disposed toward the light source and said film positioned between said inner side and light source,

said film being dimensioned and configured to fit closely but loosely within said element,

and said improved means including positioning means effective when the same is so mounted on a luminaire to position said film within said element so that a thin insulating air space is provided between said film and said inner side of said element.

2. The improved light-transmitting means defined in claim 1 wherein the portions of the film disposed between the light source and said inner side are substantially imperforate so that said film provides a removable shield which protects said inner side from accumulations of dust and the like.

3. The improved means defined in claim 1 wherein each of said element and film has an open side adjacent which is a peripheral flange, the flange of said film engaging the flange of said element when said film is inserted in said element, the interengaged flanges providing said positionmg means.

4. The improved means defined in claim 1 wherein said film has a thickness in the range from about .001" to about .012".

5. The improved means defined in claim 1 wherein each of said element and film has an open side adjacent which is a peripheral flange, the flange of said film being engaged against the flange of said element when said film is inserted within said element, said interengaged flanges providing said positioning means,

said film having a thickness in the range from about .001 to about .012",

the portions of the film disposed between the light source of a luminaire and said inner side being substantially imperforate so that said film provides a removable shield which protects said inner side from accumulations of dust and the like.

References Cited by the Examiner UNITED STATES PATENTS 2,080,120 5/ 1937 Everett 240-47 2,320,533 6/1943 Muskat et al.

2,860,059 11/1958 Molter et al.

2,917,402 12/ 1959 Sapper.

2,991,273 7/1961 Heckelhammer et al.

3,188,461 6/1965 Lipscomb 240-106 X NORTON ANSHER, Primary Examiner.

C. R. RHODES, Assistant Examiner. 

1. FOR A LUMINAIRE HAVING A LIGHT SOURCE AN LIGHT-TRANS MITTING MEANS HELD BY SUPPORT MEANS IN LIGHT-TRANSMITTING RELATION TO THE LIGHT SOURCE, IMPROVED LIGHT-TRANSMITTING MEANS COMPRISING, A BOWL-SHAPED, FORM-RETAINING ELEMENT MADE OF A TOUGH, WEATHER-RESISTANT, TRANSLUCENT PLASTIC MATERIAL, SAID ELEMENT HAVING AN INNER SIDE AND AN OUTER SIDE, A BOWL-SHAPED FILM MADE OF A HEAT-RESISTANT, TRANSLUCENT PLASTIC MATERIAL, SAID FILM HAVING A THICKNESS OF AT LEAST ABOUT 1 MIL AND BEING SUBSTANTIALLY OPAQUE TO ULTRAVIOLET RADIATION, SAID FILM BEING SEPARATE FROM SAID ELEMENT AND BEING REMOVABLY INSERTABLE WITHIN SAID ELEMENT, SAID ELEMENT AND FILM BEING DIMENSIONED AND CONFIGURED TO BE MOUNTED IN LIGHT-TRANSMITTING RELATION TO THE LIGHT SOURCE OF A LUMINAIRE WITH WHICH THEY ARE ADAPTED TO BE USE WITH SAID INNER SIDE DISPOSED TOWARD THE LIGHT SOURCE AND SAID FILM POSITIONED BETWEEN SAID INNER SIDE AND LIGHT SOURCE, SAID FILM BEING DIMENSIONED AND CONFIGURED TO FIT COLOSELY BUT LOOSELY WITHIN SAID ELEMENT, AND SAID IMPROVED MEANS INCLUDING POSITIONING MEANS EFFECTIVE WHEN THE SAME IS SO MOUNTED ON A LUMINAIRE TO POSITION SAID FILM WITHIN SAID ELEMENT SO THAT A THIN INSULATING AIR SPACE IS PROVIDED BETWEEN SAID FILM AND SAID INNER SIDE OF SAID ELEMENT. 